Mechanical pencil

ABSTRACT

A mechanical pencil has at the forward tip portion thereof a movable cylinder made up of a lead-protecting tube and an outside tube covering the lead-protecting tube. Lead extends through the lead-protecting tube and further through a chuck provided above the movable cylinder. A ring is provided for applying a load to the movable cylinder to add to its plunging movement for withdrawing into the pencil proper, the pencil proper having the forward tip directed upward at this time. The ring is the outside of the lead-protecting tube leaving a clearance between the ring and the lead-protecting tube. The outside tube is expanded at the bottom thereof so as to retain the ring therewith at the time of withdrawing the lead into the pencil proper.

1 Aug. 12, 1975 O United States Patent Mitsuya 1 MECHANICAL PENCIL [76]Inventor: Yoshihide Mitsuya, 1,3-chome,

Higashi Nagata, Jhoto-ku, Osaka, Japan [22] Filed: Apr. 10, 1974 [21]Appl. No.: 459,854

[52] US. Cl. 401/65 [51] Int. Cl 843k 21/16 [58] Field of Search401/65-67, 40l/9294 [56] References Cited UNITED STATES PATENTS2,385,329 9/1945 Buchanan 401/65 2,532,748 12/1950 Votruba 401/653,537,799 11/1970 Sakamoto 401/67 3,804,536 4/1974 Torii et a1. 401/65Primary ExaminerLawrence Charles Attorney, Agent, or FirmWenderoth, Lind& Ponack 57 1 ABSTRACT A mechanical pencil has at the forward tipportion thereof a movable cylinder made up of a leadprotecting tube andan outside tube covering the leadprotecting tube. Lead extends throughthe leadprotecting tube and further through a chuck provided above themovable cylinder. A ring is provided for applying a load to the movablecylinder to add to its plunging movement for withdrawing into the pencilproper, the pencil proper having the forward tip directed upward at thistime. The ring is the outside of the lead-protecting tube leaving aclearance between the ring and the lead-protecting tube. The outsidetube is expanded at the bottom thereof so as to retain the ringtherewith at the time of withdrawing the lead into the pencil proper.

1 Claim, 5 Drawing Figures PATENTEU AUG 1 2 I975 SHEET FIG.1

PATENTED AUG 1 2 I975 SHEET FIG.3

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MECHANICAL PENCIL The present invention relates to a mechanical pencilprovided with an improvement in the reciprocating movement of lead inand out of the mechanical pencil proper.

In a conventional mechanical pencil having a movable cylinder at itsforward tip with a lead-protecting tube fixed therein, thelead-protecting tube is likely to break when the pencil with thelead-protector projected therefrom accidentally hits the ground or anyother solid object. Also, a mechanical pencil having such a mechanism asabove mentioned usually retracts the lead by pushing a push buttonattached to the pencil to loosen a lead-trapping chuck, thereby allowingthe lead to be pushed into the pencil directly by a finger and the like.Such action very often causes the lead to break.

As a countermeasure, a method has been tried which withdraws thelead-protector into the pencil by taking advantage of the gravity of thelead-protector itself, however this method has proven defective in thatregard because when the lead-protector has a weight heavy enough toallow itself and the lead to retract into the pencil without anypressure thereto from the outside, the lead is likely to break under theimpact coming from the lead-protector when the pencil accidentally hitsthe ground or any other solid object described hereinbefore. The presentinvention adopts a leadapplying ring fixed outside the lead-protector,thereby keeping a space between the ring and the leadprotector. Saidring has the function of giving a load to the movable cylinder, therebyallowing the leadprotector to return into the pencil when the pencil isheld vertically with the lead-protector directed upward. The ring isfurther situated so as not to collide with the lead-protector even whenthe pencil is dropped on a solid item.

The above-mentioned object of the present invention can be accomplishedby the improvement, combination and operation of every part constitutingthe present invention, the preferred embodiment of which will bedescribed in detail in relation with the annexed drawing as follows.

FIG. 1 is a longitudinal section ofa mechanical pencil in the presentinvention showing its lower portion organization.

FIG. 2 is an upside-down longitudinal view of FIG. 1 when withdrawing alead and leadprotector into the pencil proper.

FIG. 3 and FIG. 4 are magnified longitudinal sections of integral partsof the mechanical pencil shown in FIG. 1.

FIG. 5 is a longitudinal section of a movable cylinder of the presentinvention showing the second embodi ment.

In FIG. 1, the mechanical pencil 12 has a forward tip portion 11, saidforward tip portion 11 has therein a movable cylinder S. Said movablecylinder S, in the first embodiment shown in FIG. 1 and 2, comprises alead-protector 13 made of stainless steel and the like, over which isfirmly fitted an outside tube 26 made of elastic material such as rubberand the like, said outside tube 26 having an enlarged outside diameterportion 15 at the bottom thereof and having at the upper inside terminalthereof a projection 27 covering said leadportector 13 all around theperiphery thereof. Said projection 27 is smaller in inside diameter thanthe diameter of lead 28 held in the lead-protector 13 so as to give asuitable friction between the lead and the inside of the elasticprojection 27.

In a space provided at the forward tip portion 11 as mentioned above, aring 17 is adapted to fit outside said lead-protector 13, therebyproviding a clearance between said ring 17 and said lead-protector l3.Said ring 17 is situated between the bottom of the outside tube 26 andthe bottom 16 of the. inside surface 18 of the forward tip 11.

As shown in FIG. 3, the clearance (a) between the inside surface of thering 17 and the outside surface of the protector 13 is larger than theclearance (b) between the outside surface of the ring 17 and the insidesurface 18 of the forward tip portion 11.

A guide tube 19 is adapted at the lower terminal of a lead-container(not shown), and a chuck 20 is provided at the lower terminal of saidguide tube 19. An outer tube 21 is provided within the pencil 12 at thelower terminal portion 22 thereof, said outer tube 21 playing the roleof tightening said chuck 20. Said chuck 20 has elasticity, enabling itto close when it is contained within said outer tube 21 and to open whenlocated out of said outer tube 21.

A male screw of said cylindrical portion 22 at its outside screws into afemale screw adapted at the forward tip portion 11 at the inside upperterminal thereof, thereby connecting said forward tip 11 to the pencil12.

The forward tip portion 1 1 at the inside periphery 23 thereof belowsaid female screw is smaller in diameter than the outer diameter of saidouter tube 21 and larger than the outer diameter of said chuck 20 in theopened state.

In the forward tip portion 11 between said inside periphery 23 and theinside periphery 18, there is fixed a ring 25 which is smaller in insidediameter than the diameter of said movable cylinder S at the expandedpart 15 thereof and bigger than the outer diameter of said outside tube26. Also, in between the lead-container (not shown), positioned at theupper terminal of said guide tube 19 and a retaining portion 29 at thelower terminal of said pencil 12, there is a spring 30 which sustainssaid guide tube 19 together with said leadcontainer (not shown) upward.

In FIG. 5 showing the second embodiment of the movable cylinder S, saidoutside tube 26 covering said lead-protector 13 and said projection 27are formed separately but are firmly fixed with each other.

Besides the foregoing embodiments, in said movable cylinder S saidoutside tube 26 and said projection 27 can be eliminated by providingonly the enlargeddiameter portions 15 outside said lead-protector 13 andmeans for holding the lead 28 unslidably inside the lead-protector 13 byproviding a friction between the lead 28 and the lead-protector 13 atthe inside surface thereof, thereby attaining the same effect as thesaid projection 27 for retaining the lead 28.

The function of the mechanical pencil in the present invention asdescribed heretofore is given below.

When a push button (not shown), attached on the pencil 12 at the upperterminal thereof, is pushed, the lead-container (not shown) and theguide tube 19 come down toward the forward tip of the pencil and at thesame time force the spring 30 downward, thereby causing the outer tube21 to tighten the chuck 20, thus enabling it to grip the lead 28 thereinand plunge downward together. Said chuck continues to move downwardafter said outer tube 21 comes to a stop after hitting the insideperiphery 23 at the upper terminal thereof, and said chuck 20 opens asit goes out of the outer tube 21 and releases the lead from its grip.

When the push button is released, the chuck 20 in the opened state risesuntil it reaches the outer tube 21 and then closes, thereby holding thelead 28 therein again.

The lead 28 advances forward at a predetermined pace per each operationof the push button as described above, thus reaching a desired positionfor writing by way of repeating said operation. Needless to mention, itis desirable to start writing with the lead 28 projecting slightly outof the lead-protector 13 when said lead-protector 13 reaches the lowestposition in the pencil 12.

When returning this mechanical pencil to the unused state, i.e.,withdrawing the lead into the pencil, the pencil is held vertically sothat the forward tip directs upward, as shown in FIG. 2. The chuck 20 isthen opened by pushing said push button, resulting in the release of thelead 28 from said chuck 20. After releasing said push button, the lead28 and the movable cylinder S fall together under the effect of thefriction between the projection 27 and the lead 28. At this time, saidring 17 works to give a load to the movable cylinder S, thereby helpingthe movable cylinder S to fall into the pencil 12 by gravity.

Said ring 17, as described above, makes easier the withdrawal of saidmovable cylinder S into the pencil 12 at a reduced weight of saidmovable cylinder compared to convention pencil of this kind, therebyreducing the possiblity of breaking the lead under the impact of saidmovable cylinder when the pencil 12 is dropped or knocked against theground and the like.

Also, with the clearance (a) between the leadprotecting tube 13 and theinside surface of said ring 17 being larger than the clearance (b)between the ring 17 and said inside surface 18, said ring 17 will nothit the lead-protecting tube 13 and accordingly will never break thelead 28 by its own impact even in the case of such accidents asdescribed above.

I claim:

1. In a mechanical lead pencil having a forward tip with a cavitytherein for containing a movable cylinder portion comprised of alead-protecting tube extending through and beyond said tip and anoutside tube covering within said cavity for surrounding a portion ofthe end of said lead-protecting tube within said cavity, and a pushbutton controlled chuck located above said movable cylinder when saidforward tip is pointed downward for holding and controlling the movementof lead in said pencil through said lead-protecting tube in response todepressing the push button, the improvement comprising:

a ring located around said lead-protecting tube immediately below saidoutside tube covering within said cavity when the forward tip is pointeddownward, said ring having an inside radius sufficiently large that thedifference between the inside radius of said ring and the radius of saidlead-protecting tube is greater than the difference between the outsideradius of the ring and the radius of the cavity in which said ring islocated, thereby preventing said ring from contacting saidlead-protecting tube at any point; and

an enlarged portion at the bottom of said outside tube coveringimmediately above said ring when said forward tip is pointed downwardfor preventing said ring from sliding over said outside tube coveringwhen said forward tip is pointed upward, whereby pointing the forwardtip upward and releasing said chuck surrounding the lead causes the leadand the lead-protecting tube to fall into the tip of the pencil undertheir own weight and under the force of the weight of the ring exertedagainst the enlarged portion of the outside tube.

1. In a mechanical lead pencil having a forward tip with a cavitytherein for containing a movable cylinder portion comprised of alead-protecting tube extending through and beyond said tip and anoutside tube covering within said cavity for surrounding a portion ofthe end of said lead-protecting tube within said cavity, and a pushbutton controlled chuck located above said movable cylinder when saidforward tip is pointed downward for holding and controlling the movementof lead in said pencil through said lead-protecting tube in response todepressing the push button, the improvement comprising: a ring locatedaround said lead-protecting tube immediately below said outside tubecovering within said cavity when the forward tip is pointed downward,said ring having an inside radius sufficiently large that the differencebetween the inside radius of said ring and the radius of saidleadprotecting tube is greater than the difference between the outsideradius of the ring and the radius of the cavity in which said ring islocated, thereby preventing said ring from contacting saidlead-protecting tube at any point; and an enlarged portion at the bottomof said outside tube covering immediately above said ring when saidforward tip is pointed downward for preventing said ring from slidingover said outside tube covering when said forward tip is pointed upward,whereby pointing the forward tip upward and releasing said chucksurrounding the lead causes the lead and the leadprotecting tube to fallinto the tip of the pencil under their own weight and under the force ofthe weight of the ring exerted against the enlarged portion of theoutside tube.